1. Field of the invention
The present invention relates to a manually operable control valve for a breathing apparatus to allow one to alternate from a primary breathing gas supply to a secondary breathing gas supply. More particularly, the present invention relates to such a valve which is especially intended for air masks used in life support breathing systems, such as those used in scuba diving or toxic environments.
2. Description of the Prior Art
In the field of scuba diving, valves or diverting means used to alternate from one breathing gas supply to another are well known in the art. In particular, such valves or diverting means are used when a primary breathing gas supply is exhausted and it is required that the breathing apparatus is diverted to a reserve or secondary breathing gas supply. Some of the earliest air supply diverting means were actuated by a reserve pull rod, typically attached to the neck of a scuba diving air tank. These early breathing apparatus comprise a single breathing gas supply tank with a capacity of typically, 2400 psi. In operation, the single tank provides breathing gas to a diver from a primary and a reserve supply. Of the total tank capacity, approximately 500 psi of breathing gas is restricted from the primary supply, as a remaining reserve supply. Upon exhaustion of the primary gas supply, the reserve pull rod is rotated so that the reserve gas supply is engaged, as shown in U.S. Pat. No. 3,701,363 to Schuler, et al. As can be appreciated, an actuating means comprising a reserve pull rod was not equipped with means for preventing accidental engagement or disengagement of the reserve gas supply when a diver or fireman or worker in a hazardous gaseous environment or a small space (e.g., toxic waste sites, smoke filled buildings, caves and tunnels with falling rocks and debris, etc). The accidental engagement causes depletion of the reserve gas supply without the user's knowledge. This may result in leaving the user with no remaining air supply causing injury or death.
Another means for changing a breathing gas supply is the carrying of a second mask and/or mouth piece, which is connected to the secondary breathing gas supply. Particularly, in situations where a full face mask is used, generally when the primary breathing gas supply is exhausted, a diver must remove his full face mask, which is connected to the primary breathing gas supply, and then put on a second full face mask, which is connected to the secondary breathing gas supply. As can be appreciated, the removal of the primary full face mask and connection of the secondary full face mask can be cumbersome and time consuming. Moreover, when diving in toxic or hazardous locations, the removal of a primary mask cannot only be cumbersome, but also life threatening.
In addition, in certain diving situations, a diver must dive to varying and extensive depths. When diving to a particular depth and subsequently coming to the surface, it is necessary for the diver to go through decompression. On the diver's ascent back to the surface, it is necessary for him to change the gas composition in the breathing supply to avoid what is known as the bends. In order to switch or change composition of the gas, the diver must often grasp a second mask and/or regulator. However, at greater depths, visibility is poor and there is a possibility that the diver could grasp the wrong mask or regulator and inevitably engage the wrong gas supply. Intake of the wrong breathing gas supply can result in danger to the diver's life, for example, intake of the wrong gas could result in a seizure.
As can be appreciated, these prior art designs do not prevent the dangers associated with switching from a primary breathing gas supply to a secondary breathing gas supply. In the event that a diver is confronted with a hazardous situation and cannot successfully and accurately alternate from a primary breathing gas supply to a secondary breathing gas supply the end result may be serious injury or death to the scuba diver.
Therefore, there is a present need for reliable valve or diverting means of simple construction and operation that allows a diver to switch breathing gas supplies in a short period of time, e.g., a few seconds in a safe and facile manner. Further, it is desired that such a valve is constructed from only a few components with very low probability of failure.